Transformers

Problem 613: The maximum flux density in the core of a 3000/240-V, 50 Hz single-phase distribution transformer is 1.25 Tesla. If the voltage induced per turn is 8 volts, determine the cross sectional of the core in cm².

Problem 614: The net cross section of a transformer is 20 square inches. The maximum flux density is 11 kilogausses. The frequency is 60 Hz. If there are 1,000 turns in the primary, determine the primary induced emf.

Problem 615: Calculate the total magnetic flux in a 60-cycle transformer in which the induced emf per turn of the winding is equal to 2 V.

Problem 626: A 13.8 kV/480 V, 10 MVA three-phase transformer has 5% impedance. What is the impedance in ohms referred to the primary?

Problem 658: A 20-kVA, 500-V load is to be supplied by an ideal step-up autotransformer from a 400-V source. Find the current in the common winding.

What should be the kVA rating of each two transformers in an open-delta bank when the three-phase balanced load is $290.4$ kVA?

A V or open delta connected transformer bank, composed of two identical units serves a balanced $3$-phase load of $16$ kVA at $230$ volts. Solve for the minimum size in kVA of the transformers needed.

A V (open delta) connected transformer bank serves a balanced $3$-phase load of $40$ kVA at $230$ V and $0.866$ pf lagging. Solve for the minimum kVA of each transformer needed to accommodate the load without overloading.

Two single-phase distribution transformers are banked in V (open delta). If each transformer is rated $37.5$ kVA, solve for the maximum $3$-phase load that the bank can carry without overloading, considering that the load has a power factor of $0.85$ lagging.

The Utility Company supplies two single-phase transformers banked in open delta. If each transformer is rated $75$ kVA capacity, what is the maximum $3$-phase load in kilowatts that the bank can carry without suffering overload considering that the load has a lagging power factor of $0.80$.

Two identical $1$-phase transformers connected in open delta will serve a $3$-phase motor load of $250$ hp, $0.70$ pf lagging, $0.90$ efficiency. Solve for the minimum size in kVA of each transformer required to serve the load without overloading.

Two single-phase transformers in an open-delta bank served a three-phase balanced load of $290.4$ kVA. If a third transformer is added for delta operation, what percent increase in load does this represent?

Three-single phase transformers each rated $75$ kVA are banked in delta and supplying a $3$-phase load drawing $160$ kVA at $0.8$ lagging power factor. If one transformer is removed for repairs, solve for the amount of overloading of the remaining units.

What should be the turns ratio of a three phase transformer to transform $10000$ kVA from $230$ kV to $4160$ V if the transformer is to be connected $\Delta - Y$?

A bank of three $50:1$ single-phase transformers connected Y-$\Delta$ is used to step down the HV transmission line rated $138$ kV. Determine the magnitude of the step down voltage.

A power transformer rated $50000$ kVA, $34.5 \text{ kV}/13.8 \text{ kV}$ is connected wye-grounded primary and delta on the secondary. Determine the full load phase current on the secondary side.

A $69/13.8$ kV, $10$ MVA three-phase transformer is connected wye-grounded delta. What is the kV rating of the secondary winding?

A power transformer rated $50000$ kVA, $34.5 \text{ kV}/13.8 \text{ kV}$ is connected wye-wye. What are the line currents at full load?

If the secondary terminals of a 5:1 stepdown transformer is connected to the primary of a 2:1 stepdown transformer then the total stepdown ratio of both transformers is

A transformer has a maximum efficiency of 95% at a load of 100 kW. What is the constant loss of the transformer?